The objectives of this project are to determine the role of NF1 mutant alleles in the phenotype of NF1 and to dissect the biochemical pathways involved in tumor progression in NF1-related tumors. Two hypothesizes are being tested. The first is that specific features of NF1 are more commonly found in individuals who have similar NF1 mutations. The second hypothesis is that mutations occur in NF1-related tumors which affect pathways involved in tumor progression. The investigators have now collected 26 NF1 patients and DNA extraction and EBV-transformation has been accomplished in the core laboratory. NF1 mutations have been detected in five patients although only eight individuals have been comprehensively screened. Current strategies are aimed at selecting NF1 cohorts with similar phenotypes in order to increase the likelihood that a specific mutation can be detected if there are allele-specific clinical features. Several manuscripts describing this work have been published.